More and more new hobbyists simply start with Arduino when learning microcontrollers. But problem is that most important things are hidden inside processes, libraries. All you get is a place to write some prepared code and click program button to get on microcontroller. I think if you start you journey to microcontrollers then you should learn how those things work and how to program “barebone”.
As all new things you probable should start blinking LEDs with AVR using tools like AVRStudio with GCC compiler, programmer adapter and breadboard. Cl97 wrote very simple guide how to get it done. If you are Arduino fan, do same with Arduino digitalwrite() function and then compare binary size and blinking speed.